Heat the oil in a Dutch oven over medium heat. Add the garlic and sauté for 2 minutes. Transfer 1 teaspoon of the cooked garlic to a small bowl; set aside. Add the tomatoes, broth, wine, oregano, basil, and ½ teaspoon of the hot pepper sauce to the saucepan. Bring to a boil over high heat.

Reduce the heat and simmer, uncovered, for 5 minutes. Add the mussels and shrimp, cover, and simmer for 3 minutes. Add the fish, cover and simmer just until the mussels open and the shrimp and fish are opaque, about 4 minutes longer.

Meanwhile, for the olive crostini, add the olives, yogurt, and remaining ¼ teaspoon hot pepper sauce to the bowl with reserved garlic. Mix well and spread the mixture over the toasted bread. Ladle the bouillabaisse into four shallow serving bowls and top with the crostini.